(Reuters) -The Texas health department reported 259 measles cases in the state on Friday, an increase of 36 cases from its previous count on March 11, as one of the largest outbreaks the U.S. has seen in the last decade spreads.

Cases in Gaines county, the center of the outbreak, rose to 174 from 156 cases, the Texas Department of State Health Services said.

Hospitalizations in the state rose to 34 from 29.

The department has classified 257 patients as "unvaccinated or unknown", which includes people with no documented doses of measles vaccine more than 14 days before symptoms appeared.

After additional investigation into the details of individual cases, the department said that three cases previously classified as vaccinated had not received a vaccine.

(Reporting by Bhanvi Satija in Bengaluru; Editing by Devika Syamnath)