The North Korean government accuses the two American journalists of crossing into the country illegally and engaging in "hostile acts" -- charges that could draw a 10-year sentence in a labor camp.
Ling grew up in Carmichael, near Sacramento. Her father still lives there.
North Korea's top court announced it began hearing the case involving Ling and Lee Wednesday at 11 p.m. California time.
A State Department spokesman says Washington has no independent confirmation that the trial has begun. No foreign observers are being allowed to watch it.
The news blackout could mean the journalists are being used as bargaining chips. North Korea might be dragging out their trial as the communist leadership waits to see what kind of sanctions Washington and the U.N. will use to punish the nation for its latest nuclear blast and barrage of missile tests last week.
Koh Yu-hwan, a North Korean expert at Dongguk University in Seoul, said Pyongyang will likely free the reporters and treat their release as a goodwill gesture that should be reciprocated with a special U.S. envoy visiting the isolated state.
The journalists, who work for former Vice President Al Gore's San Francisco-based Current TV, were doing a story about the trafficking of women when they were arrested on March 17 near the Chinese-North Korean border. It was unclear if they strayed into the North or were grabbed by border guards who encroached on Chinese territory.
Current TV has remained silent on the story.
An employee of Current told Gawker the company ordered all employees to remain silent on the matter as soon at the two were detained and they have stuck to that policy ever since.
But on Friday, State Department spokesman Ian Kelly did not rule out the possibility of Gore being sent to take part in the negotiation for their release.
"It's a very, very sensitive issue, I'm not going to go into it," Kelly told reporters.
When asked if Gore himself was the one to raise the issue of him going, Kelly refused to get into any details on discussions that may or may not have taken place.
Ling's sister, well-known journalist Lisa Ling, has spoken to her sister once on the phone. She said in an interview earlier this week, "They're very, very scared."
Lisa Ling broke down in tears as she addressed a crowd of supporters Wednesday night in Santa Monica, the night the trial is said to have started.
If found guilty, the women won't be allowed to appeal because the case is being heard in Pyongyang's high court, where decisions are final, said Choi Eun-suk, a professor on North Korean legal affairs at the Institute for Far Eastern Studies at Kyungnam University in South Korea.
Choi said the reporters would likely be sentenced to more than five years but less than 10 years in a labor prison. Then the negotiations with the U.S. would begin, he said.