Four persons, allegedly BJP workers, have been named accused in the FIR lodged in connection with an explosion in Chapra on April 25.Bhupendra Singh and Vimesh Singh were killed when bombs they were making allegedly for use during polling in Chapra, exploded at Samkauria village under the Ishwapur police station in Bihar’s Saran district.Police said Bhupendra Singh and Vimesh Singh were allegedly BJP workers. Tuna Singh and Jagdish Singh of Samkauria have also been named accused. —PTI