Washington, March 25 : At least two people were killed and multiple others remain unaccounted for after an explosion and subsequent fire ripped through a chocolate factory in the US state of Pennsylvania. The incident was reported at the R.M. Palmer Company in West Reading, Berks County, at about 5 p.m. on Friday evening, reports Xinhua news agency. At least six others have been hospitalised, and nine are still missing, according to emergency officials. The cause of the explosion is yet to be ascertained. Images posted on social media showed massive flames tearing through the building and a tower of smoke after the arrival of fire fighters. Richard M. Palmer Sr. founded the company in 1948 selling a handful of chocolates, including bunnies, NBC News reported. R.M. Palmer Company now employs 850 people and sells more than 500 seasonal products, according to the company's website. /IANS