The two people would not describe the material found on the shirt but said DNA matched a sample from Strauss-Kahn, who submitted to testing after his arrest more than a week ago. He denies the maid's allegations.
Testing was being performed on other items, said the two people, who were not authorized to speak publicly about the matter and spoke to the AP on Monday on condition of anonymity.
During their investigation, authorities cut out a piece of carpet and swabbed sinks and other surfaces in his hotel room.
Investigators told the AP they believed the carpet in the hotel room may contain Strauss-Kahn's semen, spat out after an episode of forced oral sex by the maid.
The forensic evidence is the first to link Strauss-Kahn to the woman - and it's also on track with what his lawyers have suggested would be his defense.
Strauss-Kahn's attorney Benjamin Brafman declined to comment on Monday. At a court hearing last week, he told a judge that forensic evidence developed in the investigation "will not be consistent with a forcible encounter" - leading to speculation that Strauss-Kahn's defense would argue that it was consensual.
New York Police Department spokesman Paul J. Browne and the Manhattan district attorney's office wouldn't comment.
The one-time French presidential contender has been charged with a criminal sex act, attempted rape and sexual abuse and is free on $1 million bail, under house arrest at a lower Manhattan apartment.
He's been accused of attacking the 32-year-old West African immigrant on May 14 in his luxury suite at the Sofitel hotel near Manhattan's Times Square. His lawyers say he's innocent.
Staff at the Sofitel told authorities that the 62-year-old Strauss-Kahn had made passes at them the day before the attack was reported, including flirting with a clerk and calling another employee to ask her up to his room, according to a third person with direct knowledge of investigators' interviews with staff.
Strauss-Kahn had flirted with one female staff member who accompanied him to his suite to make sure his accommodations were satisfactory after he checked in on May 13, the person said. Later, he phoned the desk clerk who had checked him in, asking her if she would like to get together with him when she got off duty, the person said. The desk clerk refused, saying she was not allowed to socialize with the VIP guest, the person said.
That person also wasn't authorized to speak publicly and spoke to the AP on condition of anonymity.
On Monday, lawyers for Strauss-Kahn continued to search for new housing for their client as he awaits trial. His bail agreement hit a snag late last week after tenants at the Upper East Side apartment building chosen for his house arrest refused to allow him, citing unwanted media attention.
Strauss-Kahn has been staying at a temporary location under watch by armed guards with Stroz Friedberg, the same company that guarded disgraced financier Bernard Madoff. It wasn't clear when he would be moved. French and U.S. media have been staking out the building where Strauss-Kahn spent the weekend after he was released from his Rikers Island jail cell.
He resigned last Wednesday from the IMF.
His attorneys have described Strauss-Kahn as a loving father and family man. They say his actions after the attack was reported are not those of a guilty man eager for a quick escape. He left the hotel, had lunch and then phoned later to ask if he'd left anything behind. When hotel staff said he had left his cellphone, he told them exactly where he was: at John F. Kennedy International Airport on a flight bound for Paris. Authorities pulled him from the jetliner.
Associated Press writer Tom Hays contributed to this report.