The agency said in a statement that it was withholding additional comment while an investigation continues.
ABC News, citing law enforcement sources, said the laptop contained floor plans for Trump Tower, details on the criminal investigation of Hillary Clinton's use of a private email server and other national security information.
The New York Daily News, citing police sources, said authorities had been searching for the laptop since it was stolen on Thursday morning from the agent's vehicle in the New York City borough of Brooklyn.
Some items stolen with the laptop, including coins and a black bag with the Secret Service insignia on it, were later recovered, the newspaper reported.
The agent also told investigators that while nothing about the White House or foreign leaders is stored on the laptop, the information there could compromise national security, the Daily News reported.
"There's data on there that's highly sensitive," a police source told the newspaper, adding: "They're scrambling like mad."
Separately CNN, citing an unnamed US Secret Service source, reported on Friday that a California man who scaled the White House fence last week was on the property's south grounds for at least 15 minutes before he was captured.