MOSCOW (AP) — The U.S. ambassador to Russia said Monday that she was able to visit the Wall Street Journal reporter who was detained more than two weeks ago on charges of espionage.

Ambassador Lynne Tracy said that she visited Evan Gershkovich in Moscow's Lefortovo Prison, notorious for harsh conditions, and “he is in good health and remains strong."

It was “the first time we’ve been permitted access to him since his wrongful detention more than two weeks ago,” she said on Twitter. “We reiterate our call for his immediate release.”

Gershkovich, 31, his employer and the U.S. government all deny he was involved in spying.

Deputy Foreign Minister Sergei Ryabkov said last week that a possible prisoner exchange for Gershkovich could take place, but only after his trial is completed. No date has been set for that.

It’s not clear how long the investigation could last, but other espionage cases have lasted for a year or more.

In December, American basketball star Brittney Griner was exchanged for Russian arms dealer Viktor Bout following her trial and conviction on drug possession charges. She had been sentenced to nine years in prison and ended up spending 10 months behind bars.

Another American, Michigan corporate security executive Paul Whelan, has been imprisoned in Russia since December 2018 on espionage charges that his family and the U.S. government have called baseless.

Gershkovich could face up to 20 years in prison if convicted.

Russia’s Federal Security Service arrested Gershkovich in Yekaterinburg, Russia’s fourth-largest city, on March 29. He is the first U.S. correspondent since the Cold War to be detained in Russia for alleged spying.

The service accuses Gershkovich of trying to obtain classified information about a Russian arms factory.