The New York Times said Wednesday that four of its journalists reporting on the conflict in Libya were missing.

Editors said they were last in contact with the journalists, who were reporting from the northern port city of Ajdabiya, on Tuesday morning New York time. And despite secondhand reports that they had been swept up by Libyan government forces, the paper said it could not confirm that information.

“We have talked with officials of the Libyan government in Tripoli, and they tell us they are attempting to ascertain the whereabouts of our journalists,” said Bill Keller, executive editor of The Times. “We are grateful to the Libyan government for their assurance that if our journalists were captured they would be released promptly and unharmed.”

The missing journalists are Anthony Shadid, the Beirut bureau chief and twice winner of the Pulitzer Prize for foreign reporting; Stephen Farrell, a reporter and videographer who was kidnapped by the Taliban in 2009 and rescued by British commandos; and two photographers, Tyler Hicks and Lynsey Addario, who have worked extensively in the Middle East and Africa.

Mr. Keller said there was some speculation that they had been detained at a government checkpoint between Ajdabiya and Benghazi, a rebel stronghold in eastern Libya. If that is the case, he said, they would eventually be taken to Tripoli. “Beyond that, we’re still pretty much in the dark,” he added.

The uprisings in the Arab world have made the region a perilous place for journalists. During the revolt that toppled Hosni Mubarak in Egypt, journalists were assaulted, accosted, detained and killed. Two Times reporters were detained there and eventually released unharmed. Lara Logan of CBS News was sexually assaulted by a group of men. An Egyptian reporter was shot and died.

Journalists’ safety in Libya has become only more uncertain since the month-old revolt began. Last week, the BBC reported that four of its journalists had been detained by Col. Muammar el-Qaddafi‘s security forces. They were beaten with rifles and subject to mock executions, the network said. Also last week, a cameraman for Al Jazeera was gunned down in what Al Jazeera, the Qatar-based television network, said was apparently an ambush near Benghazi.

The Committee to Protect Journalists has documented more than 300 cases of attacks on journalists in the Middle East and North Africa since uprisings began there in January. More than 40 of those have occurred in Libya.

Joel Simon, the committee’s executive director, said news organizations never have easy answers when it comes to balancing safety with decisions about how to cover stories that put journalists in harm’s way.

“In every one of these countries there are vital stories unfolding, stories of crucial significance that need to be told, so it’s understandable that news organizations are accepting a certain level of risk,” Mr. Simon said. “But how do you balance those risks? Those are very tough calls that journalists and news organizations have to make on an ongoing basis. But the starting point, I think, has to be these are crucially important stories.”

The Times, like many news organizations, has procedures in place to carefully track its journalists’ whereabouts in war zones and areas of conflict. Susan Chira, foreign editor of The Times, said that each night editors discuss plans for the following day with their correspondents, who are expected to check in regularly.

“We expect to hear from them several times a day — and so do their colleagues in the field, who are often our early-warning system of any trouble,” Ms. Chira said.

The Times picture desk requires its photographers check in at a given time each day.