UPDATED: April 19, 2013, at 4:21 p.m.

With greater Boston on lockdown as law enforcement officers hunt down the Boston Marathon bombing suspect, Harvard has canceled programming for Visitas weekend.

Associate Dean of the College John “Jay” L. Ellison wrote in an email to students at about 1:40 p.m. on Friday that "organizers are working with impacted students and their families.” He reiterated that there continues to be no known threat to Harvard’s campus.

Still, Faculty of Arts and Sciences spokesperson Jeff Neal wrote in an email Friday afternoon that the College will not reschedule the annual weekend for admitted prospective students.

Prior to canceling the event, Harvard had closed registration for Visitas weekend Friday morning. In an email sent to all admitted students Friday morning, the College advised admitted freshmen who have not yet left for Cambridge to stay put until they receive further direction.

Citing the continued closure of the MBTA and other forms of transportation throughout Boston, the Friday morning email stressed that any students in transit for Visitas should stay where they are and wait for further instruction from the University. The email warned that transportation in Cambridge and Boston is currently impossible and should not be attempted.

Neal reiterated that concern Friday afternoon.

“Students already in transit should, if practicable, return home,” Neal wrote. “We will work directly with individual students who have arrived in the Boston area, or who will soon be arriving, to determine their best course of action.”

Neal said Harvard has worked with Massport to arrange a meeting place for all Visitas attendees in Terminal E of Boston Logan International Airport. Massport has posted signage directing all arriving students to that point, where they are being greeted and redirected by Assistant Dean for Administration Noah S. Selsby ’94, Neal wrote. All admitted students will receive an email alerting them to the arrangement, he added.

That announcement comes as the surviving Boston Marathon bombing suspect, Dzhokhar A. Tsarnaev, remains armed and at large likely in the greater Boston area. Tsarnaev was last seen early Friday morning in East Watertown after a standoff with police. Law enforcement officials have surrounded what is thought to be Tsarnaev’s home in central Cambridge.

Harvard, like many other local universities and school systems, is closed for the day, and authorities have asked individuals to stay home and businesses to remain closed in Cambridge and several other Boston suburbs and neighborhoods.

“We regret this inconvenience and share your disappointment that Visitas has been disrupted. But your safety and the safety of the public is of the utmost importance to us,” the College’s early Friday email to all admitted students read. “We will be back in touch as soon as we have more information about when it is again appropriate to attempt to travel to Harvard.”

Early Friday morning, Massachusetts Governor Deval L. Patrick ’78 ordered the MBTA to halt service on all buses and trains. Amtrak announced early Friday that it would halt service between Providence, R.I., and Boston and Friday afternoon that it had extended that suspension through New York City. Bus companies Greyhound, Megabus and BoltBus all suspended service in and out of Boston mid-morning. As of around 8 a.m., Boston Logan International Airport expected to stay open. All taxi service within the city of Boston was suspended Friday morning, but was reinstated hours later.

An announcement posted at 6:49 a.m. on the Harvard College Office of Admissions website says that University administrators have been in close contact with Harvard University Police Department since Thursday evening. It added that the University will remain on “high alert until the situation is resolved.”