Houston: The FBI has joined a search for an Indian-American Northwestern University student reported missing since last week, according to the University police which is investigating the case.

18-year-old Harsha Maddula, Northwestern pre-med sophomore and straight-A student, disappeared on Saturday over the weekend after attending an off-campus party with friends.

Police say they've interviewed dozens and checked the student's cell phone. 

Friends from Maddula's dorm said they last saw him while leaving the off-campus party.

"They realized that he wasn't with them while they were walking to another party," said a friend of Maddula, who was with him at the party. Maddula's friends did not want to be identified due to the sensitivity of the situation.

Maddula left the party with three or four people, according to multiple sources who saw his group leaving the house, which is located west of campus.

Several sources who said they spoke with Maddula at the party recalled him as coherent - not stumbling or visibly intoxicated - as he left.

Weinberg junior Moritz Gellner, who lives at the house where Maddula was last seen, sent a statement to The Daily after the emergency alert was sent out.

"Everybody in our house has been complying with the investigation and is trying to give as much information as possible regarding what we know about the student in question," Gellner said.

"His safety is paramount and it's the most important thing that needs to be addressed and now we wish the police the best of luck in their search for the student."

Originally from the small Long Island town of New Hyde Park, New York, Maddula lived with parents Prasad and Dhanalakshmi Maddula before coming to NU last year.

"I don't know what to do," Prasad told local media, shortly after university police first notified him and his wife of the disappearance.

"I'm so scared and upset. There are no words that I can use to explain anything."

After not hearing from Harsha since Friday, Prasad called a community assistant at PARC on Sunday night, but said the CA did not know anything about his son's whereabouts.

Prasad then decided to fly to Chicago with his wife to deal with the situation directly.

"Excited to help other people. He came one week early to help freshman," said his father, Prasad Maddula.

His parents say their son, a diabetic, would never walk away of his own choosing. He had goals and dreams. 

"We just spoke to the President of the University Shapiro, he assured us he's going to do everything to find Harsha no matter what," said Prasad.