The search is being conducted by divers from the U.S. Coast Guard and local fire departments, in addition to law enforcement authorities. They are searching boats docked in the harbor as well.
"We have widened the search area because an examination of cell phone activity done by police showed that the closest cell phone tower was the one here at the U.S. Coast Guard station in Wilmette," said Alan Cubbage, vice president of university relations at Northwestern.
He said the cell phone signal-- which was a ping and not an actual phone call-- was received in the early morning hours of September 22, shortly after Maddula was last seen at an off-campus party.
Cubbage said divers are using underwater sonar to assist in the search, although he hopes that a body is not recovered and Maddula is found unharmed.
"At this time it is not known. The search is underway both in the water and in the surrounding harbor," said Cubbage.
Maddula's family, who had flown in from New York to help with search efforts, appeared visibly emotional on Wednesday.
"We can't control our emotions anymore because we don't know whether he is alive or not," said Prasad Maddula, father.
Cubbage said that there is no indication of foul play on campus or at Wilmette Harbor.
Wilmette Harbor is approximately two miles north of Maddula's residence hall on Northwestern's Evanston campus-- a 30-minute walk from the party where Maddula was last seen.
Family members said the 18-year-old, straight-A, pre-med sophomore has never vanished before.
"He just came Wednesday over here to help first-year students," said mother Dhannalakshmi Maddula. "Classes start this Thursday, but he wants to help. He's a very helping boy and he's so good. I don't know what happened."
Friday evening, Maddula was with friends at an off-campus party. He and others left around 12:30 a.m. Saturday morning, heading -- it is believed -- for another party when Maddula disappeared.
University police have interviewed those who were with him and found no leads.
Surveillance camera footage from Maddula's dorm in the heart of campus does not show Maddula on it, nor do records show he entered the building with his electronic dorm key.
ABC7 visited the site of the off-campus party house where he was last seen.
"NUPD has been to this house multiple times and we've given out all of the information we have, it's all on record," said Moritz Gellner, host of the party. He said he did not personally see Maddula there.
Maddula's family is frustrated more people who were at the party haven't come forward.
"Help his family search for him. You're his friends, right?" said Sushma Maddula, aunt. "When they're not, I feel like they're hiding something."
"No one is going to get into trouble. We understand there was a lot of underage drinking, underage drugs. I don't think that's the point. The point is that there is someone who is 19 years old who is missing," said Surekha Maddula, aunt.
Meanwhile, neighbors say the partying at the house where Maddula was last seen has continued.
"There was one last night and there was one a couple of nights ago," said Jenna Casady, neighbor. "That one also went on till two or three in the morning."
"I have no comment," said Gellner when asked about the alleged parties.
Maddula is described as:
- Male of Indian descent
- 5' 4" tall, 135 pounds
- black hair
- wearing black-framed glasses
- gray, long-sleeve sweater with white and black stitching
- dark gray pants
- brown shoes
Maddula's mother tells ABC7 that on Friday morning she had a phone conversation with Harsha. She says he was in great spirits, looking forward to the following weekend and the coming week on campus.
Maddula learned last December he has diabetes, but his parents say he had learned how to manage how to manage both his diet and what he drinks.
The family has set up a facebook page to help in the search.
The Evanston Police Department and the FBI are also involved in the search. Anyone with information is asked to call Northwestern University Police at (847) 491-3254.