US authorities have have discovered a sophisticated drug-smuggling tunnel that went from under a bed in a Mexican house to an abandoned KFC restaurant in Arizona.

Working on a tip received in April, police began trailing the owner of the abandoned building, Ivan Lopez, and arrested him after finding several packages of methamphetamine, cocaine, heroin and fentanyl in the back of his truck.

That arrest led to a search at his home and an old restaurant, where agents found a hidden tunnel that led to a house in Mexico and was large enough for people to freely walk through, Associated Press reports.

Homeland Security special agent in charge, Scott Brown, said his agency has been seeing an increase in tunnels. He said a functioning tunnel can cost cartels hundreds of thousands of dollars to build.

Authorities don’t know how long the tunnel had been in use, but Lopez only bought the property in April.

According to court documents, the government believes Lopez is a well-trusted cartel member.

He was seen taking packages out of the building several times before his arrest on 13 August, the court papers said.

Lopez is being held in federal detention without bond because he is considered a flight risk, according to court documents.