Sunni politicians on Wednesday requested an international investigation into claims that Shiite forces abused suspected insurgents. A reporter provides an update from Baghdad.

GWEN IFILL: John Burns, welcome back. What can you tell us about how and where these prisoners were discovered?

JOHN BURNS: They were discovered about a mile and a half from here in the district called Jadriyah, which also is only just across the Tigris River from the American command center in the green zone, this on Sunday night when American troops reacting to a whole series of complaints from mainly Sunni-Arab residents of the city about relatives who have disappeared into this place raided the center, although they don't like to call it that, the Americans, that is.

They went in with Iraq troops; they found 173 detainees, almost all Sunni Arabs, mostly men, some teenage boys, malnutrition, and as we learned, yesterday, tortured, so it seems, to some considerable degree with implements of torture and so forth.

Because of the fact that these appear to have been Shiite policemen or Shiite religious militiamen in police uniforms inflicting this torture on Sunni Arabs, this has, of course, further inflamed the sectarian divisions here, which were already running at a very high level.

GWEN IFILL: This was something which had been rumored to be going on for a long time but there wasn't any proof of it, I guess.

JOHN BURNS: You know, when you hear American officers as we did today at a rather high level of the command talking about the problems that they confront over issues like this, you have the feeling that it is really kind of Ali Baba's cave that they are operating in here, separating truth from fiction and can be extraordinarily difficult in a society which under Saddam Hussein was always awash with rumor and conspiracy.

There have been these rumors of secret detention centers, of militias carrying out extrajudicial and judicial killings, death squads and attacks for many months.

What we were told today by one of the most senior generals in the command was that they have investigated all of these reports that have reached them and have not been able, until this instance, to actually run to ground a detention center.

Now there are reports that some of these detention centers are mobile in the sense that people are held in the basement here, moved to a basement somewhere else, and who knows, possibly some of them killed.

It is an extremely difficult thing in Iraq in general to separate truth from fiction and I think this is a very good example of that.

GWEN IFILL: As you know here in the states the discussion about torture has been this week, at least, about what U.S. forces may or may not be engaged in.

To make a distinction, this is not what about U.S. forces are doing; this is alleged to be about what Iraqi forces are up to?

JOHN BURNS: That's exactly what it is about. The allegation is that policemen under the authority of the interior ministry, which is run by a Shiite minister in the Shiite religious-dominated transitional government, that these police officers, perhaps belonging to a Shiite religious militia themselves, inflicted this torture on Sunni Arabs. Now, the Americans have reacted to this with tremendous vehemence and unusually, given how careful they've been in the past year and a half to try and put, as they say, an Iraqi face on the government here. This is, after all, a formerly sovereign state.

Unusually, the American commander here, Gen. George Casey and the American ambassador, have taken the lead very publicly in going to the Iraqi prime minister, Ibrahim al-Jaafari, and saying do something about this; investigate it, get to the bottom of it.

Now, of course, it has to be said that American officers one would hope, in any case feel outraged by this. But all American officers, all American troops operate, of course, under the shadow of the Abu Ghraib Prison scandal and other prisoner abuse scandals that have afflicted the American forces here -- and that has further, if you will, motivated the command here to make sure that this time, on their watch, this thing is properly investigated and tracked down.

GWEN IFILL: Is there any fear in a larger sense that these allegations, should they prove to be true, would it further exacerbate Sunni Shiite tensions which exist anyway?

JOHN BURNS: Well, yes. I mean, that's the headline in all this. And that is certainly what we were hearing today even from moderate Sunni Arab political groups, including some of those who have agreed to participate in the Dec. 15 elections and already named and fielded a slate of candidates.

But there's another side to this, and that is that according to Gen. William Webster, who commands the Third Infantry Division with 30,000 troops in Baghdad, his troops within the last 24 hours since the prime minister announced the investigation at the insistence of the American command, his troops, American soldiers are hearing on the streets for the first time a kind of flood of approval from Sunni Arabs who are saying, well now, now you are showing us you are here not to favor one side, that side being of course the Shiite majority who have taken power under the transitional government.

Gen. Webster, and he is not alone in this in the American command feels that, as the Chinese say, out of all things bad something good, that there may be an undercurrent here that will actually bear fruit in terms of Sunni Arabs perhaps thinking again what America is really up to here.

GWEN IFILL: So has Prime Minister al-Jaafari set a deadline for the report on this investigation?

JOHN BURNS: He has. He ordered his deputy prime minister, a Kurd, to report within two weeks and the F.B.I. and the Justice Department, along with the American military command, are going to be actively involved in this investigation providing all manner of support.

And there was a separate inquiry ordered which -- by al-Jaafari, the prime minister, for a count to be taken of all prisoners and detainees across Iraq for their locations to be determined and for a report to be made on the conditions under which they are held.

GWEN IFILL: John Burns, as always, thank you.

JOHN BURNS: It's a pleasure.