An explosion at a fireworks factory in the state of México left six dead and at least five injured on Friday, just days after the country's holiday season kicked off in earnest.

The explosion occurred around 11:00 am in the ejido of San Lorenzo Octeyuco, Jilotepec, according to the Secretariat of Security of the State of Mexico (SSEM), which issued a first report of four dead and seven injured, two of whom died later at the General Hospital of Jilotepec.

Emergency workers were immediately dispatched to the scene, including 70 state and 20 municipal police officers; experts from the Emergency Services of the State of Mexico (SUEM) to provide care for the injured; Civil Protection workers to put out the fires, and elements of the Mexican Public Prosecutor's Office.

According to police officers close to the case, four wounded were taken to the General Hospital of Jilotepec, while three were transported by helicopters from the Rellampagos Group to the Adolfo López Mateos Hospital, located in the Mexican capital, because they required special attention.

Residents reported that the explosion rattled windows a kilometer away.

"At about 11:00 in the morning, we heard the explosion, it was so strong it shook the earth, when we peeked out the window to see what was happening, we saw smoke coming out of the buildings," a local resident reported.

Officials said fireworks were being manufactured and stored on the property. Of the six buildings on the site, four were severely damaged.

"It was very bad, more so for the people who died... but it's not the first time this has happened, there have been accidents before because a lot of pyrotechnics are made and handled there..." said another neighbor.

Fireworks are a mainstay of holidays in Mexico including Christmas, New Year's Eve and the country's 12-day celebration of the Virgin of Guadalupe. However explosions are relatively common amid what is criticized as lax safety practices and oversight of the industry.