Police are investigating the death of a Massachusetts Institute of Technology student who died in the city this weekend in what appears to be an alcohol-related incident.

The body of James Albrecht, 21, was found by police on the roof of a building near Union Square on Sunday at about 8 p.m., police officials said.

A friend of Albrecht’s at MIT, Arash Sercowsi, said Albrecht left a message on his instant-messaging account that said he planned to attend a party. “Online he was away for 40 hours, and his away message said he was going to a birthday party,” Mr. Sercowsi said. “That was Friday night, and then the last person to see him saw him Saturday at 3 a.m.”

Albrecht, who was working as an intern for the summer at an investment and technology development firm, D.E. Shaw & Co., was out Saturday night at Banc Café on 30th Street and Third Avenue at a birthday party, a friend who grew up with Albrecht in Naperville, Ill., David Huang, 21, said. “People who were at the party told me he wasn’t crazy,” Mr. Huang said. “They said nobody was drinking excessively.”

As the party dwindled down after 2 a.m., Albrecht left to meet some friends, Mr. Huang said.

It is unclear how Albrecht ended up in Union Square, friends said.

Albrecht’s parents flew to the city from Illinois soon after learning of their son’s death, Mr. Sercowsi said. Investigators told them that their son fell from a building at 243 14th St. and landed on the roof of a one-story building next door, friends said.

A resident in the building, who refused to identify himself, said there was a party on the top floor of the building on Saturday night.

Police officials said they were waiting for the results of an autopsy before they would comment on the investigation. The office of the medical examiner said results from the autopsy would be available yesterday. However, the office did not return several follow-up phone calls.

A police source said investigators believe the death was alcohol-related.

Albrecht was living at 5 St. Marks Place for the summer with a friend from MIT, Arthur Ni, while completing his internship. “He was having a lot of fun, he really liked his job,” Mr. Sercowsi said. “Sometimes he would talk about some of the problems he was solving and what he was doing at work.”

Albrecht’s roommate, Mr. Ni, who was out of town for the weekend, said both he and Albrecht were math and physics majors. “He was one of the smartest kids at MIT,” Mr. Ni said. “Even though he was smart, he was kind and approachable and friendly.

While Albrecht liked to go out and have fun, several friends said he was not a habitual or heavy drinker. A posting from Albrecht that was left on the social networking Web site Facebook.com advertised a party he was throwing last week in celebration of the 21st Amendment, which ended Prohibition.

According to friends, Albrecht was a teacher’s assistant at MIT, helping freshman and sophomores in differential equations classes. “Everybody who had him thought he was great,” Mr. Ni said.