A Dallas police officer is under criminal investigation after a man said he was taken to West Dallas early Tuesday, doused with pepper spray and left there.

Authorities are investigating whether Officer Michael Loeb tried to cover up the incident. He was placed on restricted duty Tuesday. Two other officers are considered witnesses in the investigation.

Police had been called because a man identified as Michael Reyes, 19, was hanging around a northwest Dallas neighborhood and asking a 77-year-old man for money, officials said.

Officer Loeb and another officer wrote in reports that they gave Mr. Reyes a ride to West Dallas and that Officer Loeb's pepper spray canister malfunctioned, accidentally spraying them and Mr. Reyes.

"When you read the officers' reports, it raises questions," Police Chief David Kunkle said Wednesday. "We're investigating first whether a crime occurred involving our officers and then, depending on what we find or don't find, it may go to Internal Affairs."

The chain of events began about 2:45 a.m. Tuesday in the 3600 block of Walnut Hill Lane when Officer Loeb responded to a "prowler call" at the home of Ernest Estrello. Senior Cpl. Antonio Lopez and a rookie he was training also responded.

Delma Franks, Mr. Estrello's daughter, said her father, who suffers from Alzheimer's, told her that the man claimed to know him and demanded that he open the door, but Mr. Estrello did not recognize him. "Daddy refused to open the door," Ms. Franks said.

Officer Loeb and Cpl. Lopez both wrote reports on the same incident, which is highly unusual.

They state that a man armed with a shotgun knocked on Mr. Estrello's door asking for money.

The reports say Officer Loeb located a man nearby matching the suspect's description – he was identified by a witness as Mr. Reyes. Cpl. Lopez wrote that no shotgun was found.

The officers wrote that Mr. Reyes told them he had been stranded in the neighborhood by friends. Cpl. Lopez also wrote that Mr. Reyes was a known gang member.

Cpl. Lopez wrote that Mr. Reyes then asked for a ride to a home in West Dallas. He said they took Mr. Reyes to North Hampton Road and Calypso Street in West Dallas, where Mr. Reyes asked them to stop at the intersection to let him out.

Officer Loeb wrote that as he walked around the squad car, he "bumped" into a side mirror, causing his pepper spray canister to malfunction. He tossed the canister to get it away from them, he wrote.

The two officers, Mr. Reyes and the rookie police officer "were struck with the pepper spray." Officer Loeb wrote that he was blinded by the spray.

"The susp [Mr. Reyes] had walked away from the [location] by the time ... Loeb could see," Officer Loeb's report said. Cpl. Lopez's report says Mr. Reyes "stated he was OK and walked off."

Mr. Reyes subsequently told the authorities that he had been taken to West Dallas, where he said the officer had pepper-sprayed him and then left.

Crime scene investigators have confiscated the officers' uniforms. They also have interviewed the rookie officer, who could not be reached for comment.

All three officers are assigned to the northwest patrol station. Officer Loeb was hired in 2004 and has no record of being disciplined.

Cpl. Lopez, a nine-year veteran, has received minor discipline for a variety of infractions, including causing a police response and using profane or indecent language. Cpl. Lopez has been temporarily removed from being able to train rookies, officials said.