FLAGSTAFF, Ariz. – Federal investigators are looking into allegations of discrimination, retaliation and a sexually hostile work environment in the Grand Canyon’s river corridor.

A group of 13 former and current Grand Canyon employees sent a letter to the Interior Department in September, alleging abuses of women during the past 15 years and prompting an investigation by the agency’s Office of Inspector General.

The agency formally requested the investigation after receiving the letter that also was sent to members of Congress in Arizona, National Park Service spokeswoman April Slayton said. The agency takes “allegations of this nature and all personnel-related matters seriously,” she said.

Agents from the Office of Inspector General have been conducting interviews. Spokesman Kris Kolesnik declined comment Monday.

Grand Canyon National Park manages 280 miles of the Colorado River, providing emergency and medical services, as well as guiding researchers, politicians and students on river trips that can last a week or longer. Commercial and private river trips are run through different systems.

According to the letter obtained by The Associated Press, Grand Canyon employees who conduct the river trips have requested sexual favours from women, retaliated against them when they were rebuffed, engaged in heavy drinking and blamed the victims when they complained.

The letter addressed to Interior Secretary Sally Jewell said that women have been threatened, fired and had their reputations damaged and work sabotaged when they reported abuses to management in the past.

“These horrendous working conditions and the retaliatory actions against the women must be stopped,” the letter states.

The letter requests that the river-outfitting duties of staff in the river corridor be separated from emergency services to create a balance of power and make it easier for park service employees to do their jobs. It also requests that anyone found to have violated the law or park policies and regulations be held accountable.