HOUSTON — The Houston Police Department is spending $2 million in overtime to have more officers patrol hot crime spots after a spike in homicides over the past two years.

Mayor Sylvester Turner said that in response to the increase in violence, he and acting Police Chief Martha Montalvo mobilized more police resources, including community agencies, and assigned more officers to street patrols.

“I authorized several actions, including an extra $2 million for police overtime, an additional cadet class, the shifting of 175 officers from desk jobs to the streets and a crackdown on gangs and Kush (synthetic marijuana),” Turner said in a statement.

Meanwhile, senior police officials are performing weekly reviews to check if a focus on gang and narcotics activity and domestic violence is reducing the number of shootings and other major crimes, the Houston Chronicle reported (http://bit.ly/2cVvQLS ).

The cause of the spike in homicides isn’t clear, Turner and others studying the violence said. Houston had 303 homicides last year, which far exceeded the 198 it had in 2011.

While homicides were expected to decrease in 12 of the 30 largest U.S. cities this year, that hasn’t happened in Houston and several other cities, said researchers at the Brennan Center for Justice at New York University’s law school.

Homicides are expected to rise by 13 percent this year, with Chicago, San Antonio, Austin, Dallas, San Diego and San Jose, California, expected to see big increases. Houston is expected to finish the year with 345 killings, a 14 percent increase from last year, the Brennan Center projected.

Cities such as Chicago and Houston have affluent sections but also neighborhoods where crime flourishes because of festering socioeconomic problems, said Brennan Center attorney Ames Grawert.

Despite the increases, the New York University researchers say crime will remain at historic lows overall nationwide.

“The key takeaway for us is when you look at increasing violent crime, it’s not a national issue,” Grawert said. “It’s an issue concentrated in a few cities, and in some cities in a few neighborhoods in particular with higher-than-average unemployment and poverty.”

However, the Houston Police Department said in a statement that its analysis “has shown many of the homicides have a gang and narcotic element.” Domestic violence involving drugs, alcohol and mental illness account for about 16 percent of Houston’s killings, according to the police statement.

Information from: Houston Chronicle, http://www.houstonchronicle.com