The father of Anthony Shadid, a New York Times correspondent missing in Libya, said his son told him "not to worry" Monday, one day before he and three journalists disappeared.
"I told him it's so crazy there, no one knows who's friend, who's foe," Buddy Shadid told the Associated Press. "But he said he knew what he's doing. We're all just praying for his safety."
Anthony Shadid, Stephen Farrell, Tyler Hicks and Lynsey Addario were reporting on the fighting in the eastern part of the country, the Times said in a statement Wednesday.
Buddy Shadid said his son was tired Monday and living on cans of tuna but planned to spend another week in Libya.
Times Executive Editor Bill Keller said on Twitter: "Four of the best journalists I know, missing in action. Libyans say if they're in [government] custody, they will be freed."
The reporters were last in contact with their editors Tuesday morning. According to the newspaper, secondhand reports said that Times reporters and photographers had been swept up by Libyan government forces in the town of Ajdabiyah, which could not be confirmed.
The journalists and a handful of others had been working there extensively and had documented heavy shelling and airstrikes and Gadhafi troops moving into the city during the day Tuesday, only to be moved back Tuesday night.
"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," Keller said in the statement. "We are grateful to the Libyan government for their assurance that if our journalists were captured, they would be released promptly and unharmed."
Keller told the AP today that there were unconfirmed reports that the journalists had been detained at a government checkpoint between Ajdabiya and Benghazi, a rebel stronghold.
The missing reporters are experienced at war coverage: Shadid, the Beirut bureau chief and two-time winner of the Pulitzer Prize for foreign reporting; Farrell, a reporter and videographer who was kidnapped by the Taliban in 2009; and photographers Hicks and Addario, who both worked extensively in the Middle East and Africa.
"Their families and their colleagues at The Times are anxiously seeking information about their situation and praying that they are safe," Keller said.
The White House urged the Libyan government Wednesday to refrain from harassing or using violence against journalists, who have come under fire multiple times in Libya since the revolution there began.
An Al Jazeera Arabic cameraman was killed Saturday when gunmen followed his car to the edge of Benghazi, the opposition stronghold, and opened fire in an apparent targeted attack.
The driver for a German journalist was killed Tuesday when he crossed the frontline and was attacked. And in the western half of the country, where journalists were supposed to operate under the strict watch and control of Gadhafi officials, BBC and Guardian journalists have been arrested, subject to mock executions and held by security forces.
Ajdabiyah has become the frontline in the past few days for both journalists and opposition fighters.
The city of 140,000 is a key crossroads from which highways lead to both Benghazi and the Egyptian border. The fighting continued Wednesday in and around the city.
Gadhafi's forces felt confident enough to bring journalists in Tripoli all the way to Ajdabiya's gates. They reported seeing truckloads of ammunition and equipment, presumably to make an even larger push today to try to retake the city.
ABC News correspondent Nick Schifrin and the Associated Press contributed to this story.