No surprise: Expect tighter security at July Fourth celebrations on the Esplanade

Police and parks officials file into Oval for press conference on July Fourth security.

Well, maybe one surprise: The Mass. Ave. bridge will be shut at 4 p.m. so that some sort of fireworks-related display can be done from it, state officials announced today.

State Police said fireworks attendees can expect bag checks, prohibitions on many items and far greater police and camera surveillance of the Pops concert and fireworks.

Everybody entering the Oval in front of the Hatch Shell - and the lagoon - will be subject to bag checks. Prohibited completely: Backpacks, cans and glass bottles, coolers on wheels, pre-mixed drinks and grills. Allowed: Liquids in sealed plastic containers no greater than 2 liters, tents or canopies of up to 10' by 10' with no sides, blankets and tarps up to 10x12 and folding chairs. Also, you'll have to bring all your personal belongings in a clear, plastic bag (you can put your purse in the bag).

But it gets even more restrictive at 4 p.m., when State Police will bar all items except chairs, tarps and blankets.

State Police say they'll have more troopers - all in yellow vests - patrolling the grounds, along with a larger number of undercover troopers and federal agents. And smile: State Police are installing more surveillance cameras than ever before.

At the July 3 rehersal concert, no tents or canopies will be allowed.

The fireworks this year will begin at 9:30 p.m., rather than 10.

• More details from State Police