A majority of multifamily developers report construction projects have fallen behind schedule because of disruption caused by the COVID-19 pandemic, according to an industry survey.

The National Multifamily Housing Council said 70 percent of members responding to a survey reported delays in construction starts, compared with 59 percent at the end of March. Overall, 56 percent reported apartment projects under construction had fallen behind schedule.

Top factors contributing to the delays included 77 percent of respondents that reported permitting issues, 44 percent with labor constraints and 28 percent with material shortages, NMHC said.

Most construction projects in Boston have been shut down since mid-March by Boston Mayor Marty Walsh, but Gov. Charlie Baker has allowed housing construction to continue on a statewide basis unless local communities enact their own restrictions.

According to the NMHC survey conducted April 9-14, nearly half of developers are sourcing materials from alternate locations and 63 percent say in-person inspections and approvals are being replaced by virtual methods.