Some of the I-93 protesters were wearing diapers — an indication they intended to block the highway for hours — state police said this afternoon after the demonstrations that roiled morning traffic, diverted ambulances and led to 29 arrests.

“Several of the protesters from Milton scene were found to be wearing adult diapers,” Massachusetts state police spokesman David Procopio said. “Their plan, obviously, was to stay on the highway for a long time.”

Starting at about 8 a.m. today, protesters — who said they were demonstrating to call attention to racial injustice — cut off northbound traffic on Interstate 93 headed towards Boston starting in Milton, and southbound 93 traffic starting in Medford. Some chained themselves to barrels filled with concrete.

Boston Mayor Martin J. Walsh today blasted the expressway protests.

“I think by upsetting and confusing and scaring a lot of people is not the way to get your message across,” Walsh said. “From what I understand, a lot of the protestors did not live in the city of Boston, did not live in the state of Massachusetts. My message to you if you are coming to this state to disrupt things, don’t.”

The Massachusetts state police colonel today called for legislation to block such highway sit-ins.

“I think we have to look at, perhaps, some legislation that would look at the interstate highway system in a different way,” Massachusetts state police Col. Supt. Tim Alben said. “Think about everything that is going on in the world today, not just here in Boston or in our country. Think about terrorism events. Now we have an unmarked van that is going to stop on an interstate highway and unload three large barrels with an unknown material — what are you thinking as a citizen out there using the interstate? What’s going through your mind when you see this kind of action and activity?”

It took hours for all lanes of traffic on the expressway to reopen. At least one ambulance was delayed and at least one was diverted, according to public safety officials.

“In the state police or Boston police department or any police department in Massachusetts or across this country we clearly understand First Amendment rights and we respect those and I think we give great leeway for people to go out there and express those rights and we have over the course of the last month,” Alben said. “If you go out to an interstate highway you are endangering your lives, you’re endangering the lives of those people that are on the highway and you’re endangering the lives of people who are in neither one of those places that you don’t know any you can’t account for,” he said. “There are in every one of these situations consequences that you can’t even anticipate.”

A release sent out by a group claiming to be the organizers of the sit-in said it was designed to protest racial injustice.

“Activists have shut down Interstate 93 Southbound and Northbound during morning rush hour commute into Boston to ‘disrupt business as usual’ and protest police and state violence against Black people,” states the release.

The statement said the protest was intended “to confront white complacency in the systemic oppression of black people in Boston.”

“Today, our nonviolent direct action is meant to expose the reality that Boston is a city where white commuters and students use the city and leave, while black and brown communities are targeted by police, exploited, and displaced,” protester Katie Seitz said in the statement.

Failure to indict white police officers blamed for the recent deaths of black men in Ferguson, Mo., and New York City have led to protests nationwide.

“I think the way to get your message across is by picking up the phone and calling the mayor of Boston and having a conversation,” Walsh said. “I’m willing to talk to anybody about any issue out there.”

He added: “I am not sure exactly who this group was. I know Black Lives Matter had been a group associated with this group. I don’t necessarily think this was Black Lives Matter. This might have been another type of occupy movement that’s coming to Boston. … From what I understand, a lot of the protestors did not live in the city of Boston, did not live in the state of Massachusetts. My message to you if you are coming to this state to disrupt things, don’t.”

The 29 people arrested at the two protest sites will be arraigned at Somerville District Court and Quincy District Court.