TIJUANA, Mexico — The Cameroonian men who share 10 mattresses on the floor of a third-floor apartment above a barber shop walk every morning to the busiest U.S. border crossing with Mexico, hoping against all odds that it will be their lucky day to claim asylum in the United States. Their unlikely bet is that a sympathetic Mexican official will somehow find a spot for them.

“I go because if they open up, I’m in,” said Rashidou Hdzekasaah, 35, who has been idled in Tijuana for two months and still has more than 6,000 names ahead of him on a waiting list to claim asylum at the San Diego crossing.

English-speaking Cameroonians fleeing atrocities of their French-speaking government helped push Tijuana’s asylum wait list to 10,000 on Sunday, up from 4,800 just three months earlier. At the same time, the U.S. is returning more Central Americans to Mexico to wait for dates in U.S. immigration court, putting asylum seekers in an unexpected, prolonged period of uncertainty.

Based on U.S. government figures and reporting by The Associated Press, at least 50,000 migrants who have reached the U.S. border with Mexico are on a waiting list for an initial attempt to seek asylum or waiting for a court hearing in the U.S. after being sent back.

The figure represents a dramatic increase from earlier in the year. It is unknown how many have entered the U.S. illegally, decided to settle in Mexico or gone back to Central America.

The long waits are testing the patience of some asylum seekers and residents in border cities.

More than 100 Cameroonians blocked the path of the government immigration vans last month, demanding more transparency about who gets accepted from the wait list to request asylum. It came after several days on which the U.S. accepted no claims. People getting called now have been in Tijuana about 3 1/2 months, but the wait is expected to lengthen.

Turning Mexico into a waiting room for U.S. asylum seekers may be the Trump administration’s most forceful response yet to a surge of migrants seeking humanitarian protection, many of them Central American families. The effort is part of a broader crackdown on immigration, subject of a polarizing debate that became even more pitched after the discovery of an anti-immigrant screed tied to a man charged with killing 22 people in El Paso, Texas, on Saturday.

Mexico, responding to President Donald Trump’s threat to raise tariffs, agreed in June to rapid expansion of a new U.S. policy to make asylum seekers to wait in Mexico while their cases wind through clogged U.S. courts. U.S. Customs and Border Protection acting Commissioner Mark Morgan said Thursday that more than 30,000 people have been returned to Mexico since the policy was launched in January.

Many others haven’t even reached the first step toward asylum. Lines began to swell last year when the Trump administration limited the number of cases it accepts each day for processing, leaving it to Mexican agencies, volunteers, nonprofit organizations and immigrants themselves to decide who fills available slots. U.S. authorities say the practice, called “metering,” responds to an inability to handle everyone at once.