The fourth round of the recycling outreach program has begun in Scarborough.

Because the program in the spring had “considerable success,” the town wrote in Facebook post, the partnership with ecomaine will continue.

Ecomaine interns, focusing on a portion of Thursday’s trash pickup route, will check recycling bins for recyclable and nonrecyclable items. Bins will be marked with one of three tags: green, bins that contain recyclables only; yellow, bins that contain a few nonrecyclable items; and red; bins that contain too many nonrecyclable items. Bins marked red will not be picked up that week.

The number of households in the 13-week spring program whose recycling bins were given green tags substantially increased, while the households that received yellow or red tags decreased, the town said.