Midtown Manhattan skyline Office landlords in Manhattan saw basically flat growth in rents during the second quarter. (Photo: W45lin)

SEATTLE—Office-market fundamentals in the nation’s 10 major metro areas generally remained solid during the second quarter, Colliers International said Wednesday. At the same time, the firm points to a leveling off of rent growth and to a pair of key factors that suggest upward pressure on vacancy rates: tenant downsizing and new supply.