Police and fire investigators are working to uncover the chain of events leading to Monday's house explosion in southeast Lincoln, including interviews, analysis of evidence, lab tests and evaluation of financial and cellphone records. Police Chief Jeff Bliemeister said his agency is now heading a criminal investigation into the explosion that leveled Jim and Jeanne Jasa's home at 5601 S. 78th St. Investigators are focusing on the Jasas and their property in determining what led to the apparent natural gas explosion that authorities believe was triggered inside the home, Bliemeister said Thursday.