LOS ANGELES, CA (KTLA) – The FBI is assisting Mexican authorities in an investigation into the disappearance of a Los Angeles firefighter in Rosarito, Mexico, authorities said Sunday.

Francisco Aguilar, 48, went to check on his Airbnb property in the coastal city less than 20 miles south of the border in Baja California and arrived there Thursday, according to family members. His daughters said they have not heard from him since that day, and his phone has been dead.

Aguilar’s family told KTLA that Mexican authorities believe there could be foul play involved. The FBI confirmed it is assisting the investigation but did not give further details.

Aguilar was only planning to be away for a few days, family members said, explaining it’s not like him to be gone for days without saying anything. And he had traveled alone.

“He was just so happy last week, talking about how going to Rosarito is just like paradise and how he loves having this freedom and spending more time with his family and just being there,” Amaris Aguilar, one of his daughters, said.

Martha Carmona Aguilar, his mother, said she has worried about Aguilar taking trips there.

“I always get concerned about him going over there but I just want him back,” she said. “I miss my son. And I want to be sure that my granddaughters get their father back.”

Aguilar has worked with the Los Angeles Fire Department for 20 years and also served in the Army.

Family members described him as a devoted father, one reason his disappearance is so unusual.

“He’s been to every single volleyball game, every single event my whole life,” Amaris said, her voice choking. “And I just don’t know what I would do without my dad.”

LAFD is assisting the efforts to bring Aguilar home, said spokesman Brian Humphrey.

“We are aware his family is unable to locate him at this time,” Humphrey said. “We are cooperating with law enforcement efforts to find him.”