Days without potable water, hours of interrogation, sleep deprivation, and the theft of more than $20,000 in cash and equipment are among the hardships two New Yorkers say they endured as prisoners of the Chinese government during the Beijing Olympics.

“They threatened our lives, threatened the lives of people we know, of our family members, and they told us that they could get us, even outside of China,” a 32-year-old artist from Williamsburg, James Powderly, said yesterday.

He and Thomas Grant, a 39-year-old videographer from the East Village, arrived in New York yesterday morning, having been deported from Beijing on Sunday — the day of the closing ceremonies for the 2008 Games.

Two advocacy groups, Reporters Without Borders and the Visual Artists Guild, organized a rally on the steps of City Hall yesterday, where Messrs. Grant and Powderly gave accounts of what they say happened to them.

Mr. Grant said he had been in Beijing to give independent journalists and artists technical assistance in getting their work past Chinese authorities. One such artist was Mr. Powderly, who said he was at the games to highlight human rights abuses through public art installations.

The two said they and four other Americans were apprehended outside a restaurant August 19, held for questioning, and then taken to a detention facility on the outskirts of Beijing.

“We were interrogated for periods of six to 10 hours a day in holding pens,” Mr. Grant recalled. “Two days into the detention, we were shown a piece of paper written in Chinese, which none of us could read, and told that we had a sentence of 10 days given to us for a violation of Chinese law. Vague as it was, that was all we were told.”

Following pressure from the American ambassador to China, Clark Randt, and New York politicians such as Rep. Nydia Velázquez, the Chinese sent Messrs. Grant and Powderly, as well as six other Americans who had been detained, back August 24.

Once they arrived at Beijing’s airport, they were deprived of all of their cash and credit cards and told that they would have to pay for their own flights home, Mr. Grant said. He also said they found out that more than $20,000 worth of video equipment had been taken from them.

Representatives of the Chinese Embassy in Washington and of the Chinese Consulate in New York could not be reached for comment.