In a letter issued Jan. 2, the first of two letters sent by the city’s Director of Consumer Affairs and Licensing Patricia A.,Underage Emerson students who enjoy Boston’s nightlife will now be sent home early, after new restrictions were placed on nightclubs by Mayor Thomas M. Menino in response to public safety concerns.

In a letter issued Jan. 2, the first of two letters sent by the city’s Director of Consumer Affairs and Licensing Patricia A. Malone, clubs such as Avalon/Axis and Paradise Rock Club and Lounge, known for holding 19-plus nights, were “directed not to operate any underage admission events … until further notice.”

According to the letter, the provision was put in place because “underaged admission events create safety and order issues for the surrounding area, as the younger crowds have been associated with increased incidents of noise and disruption.”

Other affected nightspots include Roxy on Tremont Street and other clubs in the Theatre District and Fenway/Lansdowne Street area.

Owners of Avalon/Axis, Rumor/Venu and Who’s on First did not return calls requesting comment on the new restrictions. Paradise Rock Club and Lounge and Roxy managers also refused to comment on the letter.

The outright ban on 19-plus nights was lifted Jan. 26, but further restrictions were detailed in a second letter sent to licensees, said Jennifer Mehigan, spokeswoman for Mayor Menino. Venues may now allow patrons between 18 and 21 years old to attend a concert-style event provided it ends by 11 p.m. and no separate over-21 event follows.

If the concert will go past the cut-off time, the venue must notify the Licensing Division two weeks in advance to ask for an exemption. The Mayor’s Office will also consider requests to hold alternative events, like an open-mic night.

“Other events have been scheduled, and we just ask the licensees to give the Mayor’s Office a call if they were to hold something different,” Mehigan said.

In Malone’s second letter, licensees were directed to “refrain from underage admission events other than the concerts” described in the letter, noting that a failure to adhere to the restrictions would threaten the public safety of Boston. There was not, however, any specific punishment outlined in the letter for clubs that held events past 11 p.m.

“There were a couple of meetings with the mayor, licensees, and the Mayor’s Office of Consumer Affairs and Licensing, and on Jan. 26, a second letter went out to inform the licensees that live concerts would be allowed with an 11 p.m. cut-off time,” said Mehigan.

She added that certain incidents involving underage patrons are under investigation by the Boston Police Department, but no specific event was cited as a cause for the new restrictions.

“As to dance clubs, we are still asking that they do not hold under-21 dance events,” Mehigan said.

“I think it’s really disappointing for kids our age. Now that the dance clubs are all 21 and up, we’ve lost our thing to do on Friday nights,” freshman marketing communication major Caroline Edwards said. “It’s understandable, though. The kids that are 18 can’t buy drinks and that’s how the clubs make their money, anyways.”

Although Mehigan noted that the Mayor’s Office expects the rules to be temporary, she could not comment on a possible timeline for the restrictions.

Despite this, the majority of clubs have now eliminated any events allowing those between 18 and 20 in order to avoid confusion.

Fifty clubs in Boston host licenses to hold under-21 or 18-plus nights, which allow them to host underage events once a week, but clubs such as Roxy, Pure and Caprice have stopped hosting college nights all together.

Edwards said she didn’t think the violence problems were related to underage events. “It just depends on where you are in Boston, because there’s violence everywhere.” she said.

Other students agreed with this sentiment.

“It’s so stupid. I’m a legal adult and I can’t even go to a club and have fun with my friends,” freshman musical theater major Chris DeVita said. “This city is fueled by 18- to 21-year-olds, so it’s just not a good idea for business.”

“I don’t think it’s fair to have these new rules. At home, it’s 18-plus everywhere,” said sophomore marketing communication major Luana Suciu, who is from Romania. “I don’t go to clubs to drink. I just want to dance.”