The body was found around 9:50 a.m., spokeswoman Christine Dunn said.
The person may have been hit by southbound train No. 228, but the circumstances of the death remain under investigation, she said.
A southbound train that was scheduled to arrive at the Tamien station at 10:12 a.m. was allowed to pass through because there were no passengers on board, she said.
However, the next scheduled southbound train -- train No. 236, which was scheduled to arrive at the Tamien station at 11:07 a.m. -- is being held at the San Jose Diridon station, she said.
No northbound trains are scheduled between Diridon and Tamien stations until about 2:30 p.m. today.
The medical examiner's office is responding to the scene.
