Every morning for the past month, around 100 people gather before dawn in a Salinas parking lot. They start lining up before 4 a.m. outside Cardenas Market, a Latin American grocery store, to board two white buses bound for San Francisco, 100 miles north.

The bus riders’ destination: the Marriott Marquis hotel, whose workers have been on strike since Oct. 4. The group, largely Latino immigrants, enter through a back entrance, away from the noisy picket lines on Fourth Street. Another bus arrives from Modesto, said Carmelo, a former worker who asked that The Chronicle not use his last name.

For the rest of the day, the temporary workers clean hotel rooms and staircases, replacing some of the 2,500 full-time, unionized Marriott workers in San Francisco who have been striking for weeks at the Marquis and six other San Francisco hotels as they demand higher pay.

The lengthy strike, which has led to numerous event cancellations during a busy convention season for the city, has widened to eight cities across the country and bruised Marriott’s reputation. Now temporary workers are alleging labor violations that could leave Marriott, the world’s biggest hotel operator, open to legal claims if their accusations are found to have merit.

Marriott has said that the seven striking hotels remain “fully operational” during the strike. The company hired a contractor, Environmental Service Partners Inc. of Hayward, to find workers, according to a pay stub Carmelo shared with The Chronicle. It shows a worker was paid $17 an hour and two hours a day of “travel time” — far less than the actual time it takes to travel round-trip from Salinas for a day’s work.

The California labor commissioner’s office is investigating a Marriott hotel in San Diego, where workers are also on strike, and a Marriott contractor there called Hotel Cleaning Services. The National Labor Relations Board’s website lists a complaint it received Tuesday against Environmental Service Partners.

Three workers told The Chronicle that they haven’t been paid on time by Environmental Service Partners. The Hayward firm did not respond to requests for comment.

Maria Calles, a temporary worker, said that she hasn’t been paid for three days of work. Alejandro Lara, another worker, said he is owed pay for eight days. They spoke to The Chronicle outside of the Marriott Marquis on Tuesday before going back inside to work.

Another temporary worker, who gave his name as Damian, said he hasn’t been paid at all since beginning work on Oct. 11.

“Many people are unhappy,” Damian said. “Some haven’t been paid for a month.”

“Marriott’s vendor contracts, including its contract with Environmental Services Partners, provide that vendors must comply with federal and state employment laws,” a Marriott spokesman said in response to questions about the allegations, referring further inquiries to the contractor.

Damian and Carmelo said the two buses in Salinas sometimes get full in the morning before all workers can board. The extra workers are turned away and not paid, they said.

“One time I stood in line at 4 a.m. and the bus was full so I missed a day of work. That’s a big problem,” Damian said.

“If there’s too many people in the bus, they have to go home,” said Carmelo, who estimates that each bus holds around 50 people.

Damian and Carmelo said they were compensated for two hours of travel time a day at a rate of $17 per hour.

Katherine Fiester, a staff attorney at Legal Aid at Work, a San Francisco nonprofit that provides free legal help to workers, said it wasn’t clear whether Environmental Service Partners was required to pay for travel time.

“Someone could argue they’re required to report to a specific site in the morning” in the Salinas parking lot, she said. “If they are, that’s the job site.” California law requires that employers pay for travel from one job site to another.

The fact that workers are getting paid for two hours of travel time “makes their case stronger” for getting paid for all of it, she said. “If they’re going to be paying for some travel time, they’re admitting it’s compensable.”

Fiester, whose organization is not involved in the labor dispute, also said that if workers are working for more than eight hours a day, they would be entitled to overtime pay, equivalent to $25.50 per hour. Travel time would also count for that overtime pay.

“Unfortunately, we see these cases all too often where immigrant workers are exploited,” Fiester said. “The janitorial industry is one of the leading violators.”

Carmelo said he’s lived in Salinas for five years after moving from Puerto Rico. He previously worked in food safety. He said he learned about the job through a Facebook group and was drawn to the $17 per hour wage at Marriott, which is a few dollars higher than typical jobs in Salinas.

Carmelo said he was fired on Tuesday after speaking briefly to a Unite Here Local 2 hotel union field leader, Elizabeth Tapia, outside the Marriott Marquis. Tapia confirmed that they spoke for about five minutes.

He said he filed charges of interference and discrimination for union activity with the National Labor Relations Board Tuesday against Environmental Service Partners and Marriott Tuesday, which agency records confirm. Federal law prohibits firing an employee in retaliation for union activity.

Carmelo said Yama Anwary, director of loss prevention at the Marriott Marquis, accused him of being a “spy” for the union, which has been marching in a picket line 24 hours a day outside the hotel. Anwary didn’t respond to a request for comment and Marriott didn’t respond to questions about its employee’s conduct.

Carmelo also said he wasn’t paid for his last day of work on Tuesday.

“That sounds very problematic,” Fiester said. “If you’re fired, you need to be given your final paycheck that day.”

A National Labor Relations Board official declined to comment. The board’s website states that a decision on whether charges have merit typically takes seven to 14 weeks.

Paola Laverde, spokeswoman for the state Department of Industrial Relations, confirmed that an investigation of a Marriott hotel in San Diego, where workers are also on strike, is under way. No Bay Area Marriott hotels where workers are on strike are being investigated.

Unite Here Local 2, which represents the striking full-time workers, said the alleged violations are “deeply disappointing.”

“This is another sad example of Marriott failing to behave as the industry leader that they should be and try to position themselves as,” said Rachel Gumpert, a spokeswoman for Unite Here, in a statement.

Chronicle staff writer Susana Guerrero contributed to this report.

Roland Li is a San Francisco Chronicle staff writer. Email: roland.li@sfchronicle.com Twitter: @rolandlisf