Update (10:45 p.m.): The train has since moved and is no longer blocking vehicle traffic.
A Union Pacific freight train stopped this evening in midtown Sacramento, obstructing vehicle traffic while railroad authorities tried to determine whether rocks were thrown or paintballs shot at the lead locomotive, according to Union Pacific spokesman Aaron Hunt.
Hunt said Union Pacific dispatch received an incident report at about 8:45 p.m.
No one was injured and the locomotive was not damaged, but he said railroad authorities held the train while they investigated.
"We apologize for any inconvenience we are causing motorists or residents," he said in an email.