Cameron and Patrick visited the makeshift memorial that includes T-shirts, letters, running shoes and other items in the city’s Copley Square early Tuesday morning.

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Mass. Gov. Deval Patrick, left, accompanies British Prime Minister David Cameron up the steps into the Massachusetts Statehouse in Boston on Monday. AP

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The memorial grew in the wake of the April 15 explosions at the marathon finish line that killed three people and injured more than 260.

One suspect died in a shootout with police days later, while a second suspect is recovering in a federal prison hospital.