. >> reporter: linda spry was driving her 2012 typical route to work, when her commute took a terrifying turn. she heard a blast so loud she thought another driver crashed. >> it was very loud and sudden. >> when you heard that explosion, what did it feel like? >> it scared the heck out of me. >> reporter: she looked around she realized it was her sun roof. >> there was a hole in the center. a big piece popped out this way. >> reporter: pictures of the damage show a hole with shard glass left in the frame. here they fix about 30 broken sun roofs every month. he says usually only one of those cases turns out to be unexplained. hews hitting it with a hammer. but he says a single concentrateed hit, like a sharp rock, can make the glass shatter. >> you're not going to get hurt with that glass. it will rain on you, but you're not going to be injured. >> reporter: the glass is designed to shatter safely, the explosion is startling. we found reports of sun roofs exploding unsuspectedly across country. >> pleading sun roofs are a thing. >> reporter: national highway traffic safety administration

linda spry, a highlands ranch woman was one of them. until one day, when she was driving to work. >> it was a nice day. >> reporter: linda was driving her 2012 nissan on her typical route to work when her commute took a terrifying turn. >> i just heard this huge explosion. >> reporter: she heard a blast driver had crashed. >> it was very loud. it was very sudden. >> when you heard that explosion, what did it feel like? >> well, it scared the heck out of me. it really startled me. >> reporter: she looked around an saw there was in crash. >> but then i saw the glass just flying off the back of my car. >> reporter: she got out and realized the explosion was her sunroof. >> there was kind of a hole in the center. there was a big piece that was kind of popped out this way. >> reporter: pictures of the damage show a hole with shards of glass left >> i just thought what the heck? how does this happen? >> reporter: here at john sunroofs, owner daryl martinez fixes about 30 broken sunroofs a month. usually only one of those turns out to be unexpl

linda spry, a highlands ranch woman was e until one day, when she was driving to work. >> it was a nice day. >> reporter: linda was driving her 2012 nissan on her typical route to work when her commute took a terrifying turn. >> i just heard this huge explosion. >> reporter: she heard a blast so loud, she thought another driver had crashed. >> it was very loud. it was very sudden. >> when you heard that explosion, what did it feel like? of me. it really startled me. >> reporter: she looked around an saw there was in crash. >> but then i saw the glass just flying off the back of my car. >> reporter: she got out and realized the explosion was her sunroof. >> there was kind of a hole in the center. there was a big piece that was kind of popped out this way. >> reporter: pictures of the damage show a hole with shards of glass left in the frame. >> i just thought what the heck? how does this happen? >> reporter: here at john sunroofs, owner fixes about 30 broken sunroofs a month. usually only one of those turns out to be unexplained. they are usually made of tempered glass. martinez shows ho