No one was injured, though BSF personnel and Pakistani Rangers went into a tizzy after the powerful explosion which saw the debris scattered "in an area of 2000 square yards".
A magisterial probe has been ordered and the Pakistani side has been informed about the incident, officials said, adding a forensic team from Chandigarh has been dispatched.
Punjab police Inspector Ravinder Singh said that after the transfer of the chemical from a Pakistani truck, leakage began.
Singh said that at the time of blast, nobody was standing near the Indian tanker as it was morning time.
The Pakistani truck was unharmed and went back.
An Indian official posted at the checkpost said that possibility of mischief cannot be ruled out and things would become clear after a thorough investigation.