The police said that explosion was reported in a garbage dump behind the Pugoda Magistrate's Court, reports the Daily Mirror newspaper.
Spokesman Ruwan Gunasekera said police were investigating the blast on empty land behind the magistrate’s court in Pugoda, 40 km (25 miles).
“There was an explosion behind the court, we are investigating,” he said, adding it was not a controlled explosion like other blasts in recent days.
There were no other details of the blast.
The blast came at a time of high tension in Sri Lanka following the Easter Sunday suicide bomber attacks on the island state that killed 359 people and wounded about 500.
The Sri Lankan government has blamed a local Muslim outfit, National Thowheed Jamath (NTJ), for the deadly bombings.