NAIROBI, Kenya (CNN) -- Kenyan immigration officials on Tuesday questioned the author of a book that is highly critical of Sen. Barack Obama, Kenyan police said.
Jerome Corsi, who wrote "The Obama Nation: Leftist Politics and the Cult of Personality," left the immigration building in Nairobi several hours later and went to the airport, his publicist Ken Bueler told CNN.
Bueler, who is in Kenya with Corsi, said the writer had been picked up before he was able to hold a planned news conference about the release of his book in Kenya. He said Corsi was not detained, but that Kenyan authorities said one of his immigration forms was missing.
Kenyan police spokesman Eric Kiraithe said immigration officials had invited Corsi to answer questions on "a few issues." He said it was not a police matter.
Corsi is a staff reporter for World Net Daily, an online conservative-leaning news site. He had been in Kenya for about a week and was scheduled to leave for London on Tuesday evening, after holding his news conference.
He said he was looking into ties Obama may have had with political leaders in Kenya, where Obama's father was born.
World Net Daily owner Joseph Farah said Corsi was picked up to prevent him from holding the news conference.
"There's no question about it," Farah told CNN from Washington, D.C. "He was detained the minute he walked in this room to hold the press conference."
Farah also said there was no reason to pick up Corsi to force him to leave the country since he was already scheduled to fly to England.
"He should have left the country by now of his own accord," Farah said.
Farah said he had been in regular telephone and text-message contact with Corsi throughout his detention but lost touch with him at 9:30 a.m. ET.
Farah said Tuesday afternoon he was concerned and had been unable to obtain information from officials in Kenya.
Corsi was invited to Kenya by missionary groups in the nation, Farah said, but they had not financed the trip as far as he knew.
Obama, the Democratic presidential nominee, is wildly popular in the eastern African country, where his grandmother still lives with other family members in western Kenya. Mutatus, small buses that ferry passengers across the country, often display his image and Obama T-shirts and bumper stickers are for sale everywhere.
In 2004, Corsi wrote "Unfit for Command," a book that was critical of Sen. John Kerry of Massachusetts, the Democratic presidential nominee that year.
CNN's David McKenzie contributed to this report.