Late Wednesday, witnesses saw the BBC's Lamin Cham being picked up by what they believe was Gambia's National Intelligence Agency. The arrest was confirmed by Gambian Press Union President Madi Ceesay.
Ten other people, including two journalists, were detained Friday. Eight of them were released Tuesday.
Gambian authorities did not immediately confirm any detentions.
Gambian authorities asked the people to report to the police after their names were published in the , a government-friendly independent newspaper. The listed people who were believed to be contributing to an online publication, critical of the regime of President Yahya Jammeh.
The did not reveal its sources.
The online publication, called , is run from the United States by Gambian Journalist Pa Nderry MBai. It is believed that hackers accessed the Web site's subscribers and passed on the information.
The usually critical content of the Web site was replaced by a statement of loyalty to the government on May 22.
Gambian journalists have told VOA that it is becoming increasingly difficult to operate ahead of October's presidential elections.
Most journalists VOA spoke to wished to remain anonymous. Speaking from neighboring Senegal, former head of the Gambian Press Union, Demba Jawo, says most media are careful about what they publish.
"It is definitely not easy, because there are a lot of draconian pieces of legislation, which are not favorable to the working climate of private journalists," Jawo said. "Also, all the newspapers and radio stations are hardly critical of the government, because everybody is censoring themselves. It is not easy."
President Jammeh came to power in a coup in 1994. Press freedom groups are becoming increasingly critical of his regime, especially since leading independent journalist Deyda Hydara was killed by gunmen in 2004.
Jawo says Mr. Jammeh is intolerant of any form of opposition.
"He does not like to be criticized. Maybe he has got that mentality where everyone has to obey orders. He definitely has that in his blood. He does not want anybody to criticize him, but only to sing his praises," he said.
Meanwhile, eight civilians are on trial for treason after being accused of participating in what Gambia's government called an attempted coup in March.