Teams of Iowa State University students and other volunteers were joining trained searchers, the Civil Air Patrol and law enforcement on Tuesday to search for a missing student.

Abel Bolanos, 19, a sophomore from Rolling Meadows, Ill., a Chicago suburb, disappeared last weekend. Iowa State police said he had been drinking at an off-campus party before he disappeared Saturday between 4 and 4:30 a.m. He was last seen leaving an apartment heading south toward his dorm on foot, reported FOX affiliate KDSM.

But he left behind his keys and his car and no one can reach him on his cell phone.

"The search for Abel continues in several different areas of the Ames area," Cmdr. Gene Deisinger of the ISU police department told FOX News on Tuesday. "We're following up on several leads right now ... including some sightings from early Saturday morning."

Deisinger said officials are confident Bolanos did leave the party on foot and that he was very intoxicated. Bolanos was not upset before he left, Deisinger said.

"His level of intoxication is part of our concern for him," Deisinger said, adding that temperatures over the weekend sank into the 40s, and that the region saw much precipitation and high winds.

"The search is based on concerns on Abel's welfare," he continued, adding that police believe no foul play was involved in his disappearance.

The university said groups of 60 volunteers will assist searchers in three shifts on Tuesday.

"Our hope is that we find Abel soon," Dean of Students Dione Somerville said. "We are committing all available resources and continue to work with ISU police, other agencies and Abel's family to bring him home safely.

His sister begged for his safe return on Monday, saying he would never have disappeared on his own.

"This is not like him," Marivelle Bolanos said at a news conference outside Wallace Hall, a residence hall where her brother lives. "Our whole family back home is very concerned."

On Monday, teams of ISU students searched residential areas near that apartment complex.

The search included help from the Iowa State Patrol, which used an aircraft with heat-detection capability to search for Bolanos in Ames on Sunday night.

Area law enforcement officials have searched all the rooms in Bolanos' residence hall and the rooms of an unoccupied residence hall next to it, Deisinger said.

Someone anonymously turned in Bolanos' credit card and debit card to the bank. Deisinger told FOX News that police have talked to the person who turned those items in, and learned the location and time in which they were found.

"We are currently following up on that," he said, adding that the cards were not used.

A friend, Tanner Francisco, told KDSM that Bolanos has a history of taking quick trips but has never gone this long without calling. He was also wearing only a t-shirt and jeans when he walked back to his dorm.

Bolanos is described as 5-foot-7 tall, 165 pounds. He has short brown hair and brown eyes. He also has the words "Ancora Imparo" tattooed on his upper right arm, reported KDSM.

The Associated Press contributed to this report.