Piecemeal development of a neighborhood shopping center in Mililani Mauka is slated to be completed after a land acquisition by local development firm Alexander & Baldwin Inc.

A&B bought 4 largely undeveloped acres adjacent to a Longs Drugs store under construction, a McDonald’s restaurant, a Tesoro gas station and other smaller tenants.

The Honolulu-based company purchased the property from Mililani Mauka’s master developer Castle & Cooke Hawaii for $8.2 million.

A&B said it plans to develop 28,000 square feet of commercial space for shops and restaurants on the site, which has an existing 5,880-square-foot building occupied by a few tenants.

When the A&B project is complete, the neighborhood retail complex being dubbed Gateway at Mililani Mauka Shopping Center will roughly double in size to about 60,000 square feet, including the Longs store expected to open in June.