"There are a multitude of factors for this, including sales," said GM spokeswoman Michelle Malcho in a phone conversation with Edmunds on Thursday. "They also include product plans and product construction plans."
She added: "We have a good supply on the ground, so customers will not be affected at all."
GM is currently offering $1,000 rebates on Volt purchases or discount financing. Car shoppers can lease a 2015 Volt for $299 a month for 39 months. Pricing has not been announced on the 2016 Volt.
Malcho would not say when Volt production resumes at the Detroit-Hamtramck Assembly Plant. But she noted that the plant will continue to build other GM products, including the Chevrolet Impala, Cadillac ELR, Chevrolet Malibu and upcoming Cadillac CT6.
In California, the Volt's largest market, there are enough Volts built to supply dealers for 100 days, according to industry estimates.
The Volt recorded a steep sales decline in March, dropping 57 percent compared to March 2014. GM sold 639 Volts in March 2015.
A new Edmunds Key Insights report found that car shoppers are bypassing fuel-efficient hybrid and electric vehicles because of cheap gasoline prices.
The hybrid/electric-drive market share of 2.7 percent is the lowest March share since 2010. In 2010, there were only 22 alternative-drive models, versus 64 in 2015.
Today's national average at the pump is $2.39, compared to $3.61 a year ago, according to AAA Daily Fuel Gauge Report on Friday.
The U.S. Energy Information Administration said the average household is expected to spend $710 less for gasoline in 2015 compared with last year because of lower prices.
GM unveiled the second-generation 2016 Volt at the 2015 Detroit Auto Show. It features a new two-motor drive unit that is as much as 12 percent more efficient and 100 pounds lighter with an all-electric range of up to 50 miles.
Edmunds says: Car shoppers can get a great deal on the current Volt while they wait for the new one to arrive at dealerships.