The retrial of 21 Hindus acquitted of killing 12 Muslims in an arson attack during religious riots that swept India's Gujarat state in 2002 opened amid tight security on Monday.
Large numbers of police guarded the entrance to the courtroom on the fourth floor of the central Mumbai building where Judge Abhay Tipsay presided. Three metal detectors were in use.
Press reports Monday said the main witnesses to the arson attack on a bakery were housed at a secret location to prevent intimidation.
The special court was packed with lawyers and reporters. Seventeen of the 21 accused of murder and arson occupied two rows of seats, guarded by dozens more policemen.
Four of the accused are being tried in absentia, prosecutor Manjula Rao said.
India's Supreme Court in April ordered a retrial after key witness Zaheera Sheikh said she had been forced to retract her testimony during the original trial, held in Gujarat, because of threats by Hindu hard-liners.
The retrial was set for neighbouring Maharashtra state, of which Bombay is the capital.
Proceedings began with the questioning of Ratilal Varia, an official surveyor who described the location of the bakery, as well as surrounding buildings, in Gujarat's Baroda town.
The prosecution says nearly 1,200 people attacked the bakery.