"It was a home-made explosive device probably activated by
cell-phone and probably made with gunpowder, judging from the
smell," said Ortega.
"We noticed the dead man lost a hand and this surely happened
the instant he handled the device," he said.
Hundreds of officers in riot gear blocked roads around the bomb site and buildings were evacuated as police helicopters hovered overhead.
Felipe Calderon, the president, has deployed the army in a year-long battle with Mexico's powerful drug cartels.
Police have made several raids in the capital and arrested suspected drug gang members found with weapons arsenals.
Ioan Grillo, a journalist in Mexico City, told Al Jazeera that the cartels could not be ruled out from involvement.
"There has also been a big crackdown against drug cartels, and the cartels have been hitting back," he said.
"The Mexican drug cartels do not have a history of bombing like the cartels in Colombia did, but if we are seeing the Mexican cartels carrying out bomb attacks against police in the cities this could be a very dangerous future for Mexico."
Mexico was also hit last year by a series of bomb attacks by left-wing fighters on oil installations.
"There has been a left-wing guerrilla group who have been carrying out a bombing campaign in Mexico over the last year, called the People's Revolutionary Army, although normally their bombs are at oil installations or government buildings and they have not been targeting civilians," Grillo said.