TUCSON, Ariz. (AP) - A probe into last month's fatal shooting of a Mexican man by a Border Patrol agent near Douglas has been mishandled, according to the agency's union.

Two agents working at the Naco processing center on the night of the incident wrote memos to Tucson Sector Chief Michael Nicley alleging that the Mexican Consulate was allowed to interview some of the six witnesses before U.S. investigators.

Union officials said that would be a breach of protocol and would put the legitimacy of those witnesses' statements in doubt.

The statements - released by the office of Rep. Tom Tancredo, R-Colo. - say consular officers were brought into the processing center, left alone and allowed to speak with witnesses.

They had not yet given their statements to a Cochise County Sheriff's Office investigator and a Border Patrol official who were interrogating witnesses one by one in a separate room.

The Mexican Consulate in Douglas and the Cochise County Sheriff's Office deny the accusations.

Investigators questioned each of the witnesses before allowing staffers from the Mexican Consulate to do so, sheriff's spokeswoman Carol Capas said.

Mexican consular officials didn't begin interviewing the witnesses until midnight and after sheriff's investigators had finished, said Oscar de la Torre, the Mexican consul in Douglas.

Border Patrol officials declined to comment on the matter but said protocol requires the Mexican Consulate officials to wait until the witnesses have been interviewed by U.S. investigators, said Gustavo Soto, Border Patrol Tucson Sector spokesman.

The Arizona chapter of the National Border Patrol Council is asking that Nicley conduct an investigation into the reported breach of protocol.

The shooting occurred the afternoon of Jan. 12, about 150 yards north of the border in an area between Bisbee and Douglas.

A male agent - whose name and age are being withheld and who is on paid administrative leave - responded to a call about a group of seven people crossing the desert.

The agent took six people into custody without incident but then became involved in a fight with Francisco Javier Dominguez Rivera, 22, of Puebla, Mexico, and shot him to death, Border Patrol officials said.

Dominguez, a construction worker in Mexico, was trying to cross into the United States illegally with a group that included his two brothers and his sister-in-law, according to authorities.