Lebanon — State transportation officials say three bridges in Lebanon will undergo new inspections after a piece of concrete fell from a similarly designed bridge in southern New Hampshire early this week.

The dual bridges carrying Interstate 89 over Route 4 at Exit 19, as well as the Mascoma Street bridge over I-89, are among 16 bridges statewide that have been flagged for further scrutiny.

“We will have inspectors in the next few weeks go out and literally take a close look at the decks of these bridges,” New Hampshire Department of Transportation spokesman Bill Boynton said on Thursday.

“We don’t know at this point whether there are any widespread issues,” he said, adding the state is conducting additional inspections out of an abundance of caution.

Cars were detoured around Interstate 93 in Derry, N.H., for hours on Monday evening after concrete fell from the Route 102 bridge onto the highway below. Roughly a dozen cars ran over the debris and one was possibly struck, Boynton said. As an additional precaution, he said, the state plans to install protective shielding underneath the 16 bridges in the spring. Shielding traditionally consists of netting or wooden boards that protect motorists from pieces of concrete that become dislodged, Boynton said.

All of the bridges slated for new inspections are on the state’s “red list,” meaning they’re inspected twice yearly due to their poor condition. Other state-owned bridges receive inspections every two years.

The listed bridges also were designed with “haunches” — sections about 4 inches wide near the flanges of support beams. It was a haunch that fell from the Route 102 bridge on Monday, Boynton said.

Lebanon has seven red-listed bridges, including those that carry I-89 over the Connecticut River, Payne Road over a set of railroad lines and the Mascoma Street and Exit 19 bridges. Two bridges on I-89 crossing Hardy Hill Road were also on the list, but repair work to both began earlier this year.

According to the state’s 10-year transportation plan, the northbound bridge over Exit 19 is slated to be repaired in 2017. The plan calls for work to begin on the Mascoma Street bridge in 2023. Transportation officials expect work on the bridges over the Connecticut River in 2019.

Tim Camerato can be reached at tcamerato@vnews.com or 603-727-3223.