* Metals strike followed historic platinum stoppage
* One employer group says will not sign deal
* Concerns about wage hikes exceeding inflation (Adds deal signing, NUMSA and ANC comments)
By Xola Potelwa and Tiisetso Motsoeneng
JOHANNESBURG, July 29 (Reuters) - South African manufacturing workers started returning to work on Tuesday after accepting a wage deal from employers, ending a four-week strike that dealt a blow to growth in Africa's most advanced economy.
NUMSA, the country's largest union, signed a wage deal on Tuesday for a 10 percent annual pay increase fixed for three years for its lowest-paid workers.
The strike by over 200,000 NUMSA members had halted production at automakers and disrupted construction of new power plants in a country with a tight electricity supply.
"We are not sure whether we have full attendance yet, but there are sufficient volumes to resume production at my two plants," said Ken Manners, chief executive of SP Metal Forgings, a supplier of component parts to the auto industry.
Engineering firm Bell Equipment, which employs 2,000 workers at its Richards Bay plant on the east coast, said staff had reported for the early morning shift, while General Motors South Africa expected to run at normal production levels from Wednesday.
Construction company Group Five said most employees at its affected businesses had returned, adding it would take the rest of the week to refill its steel supply chain.
"Due to the severity of the strike, its impact will influence current and future business plans within the South African steel sector," Group Five said.
However, not all companies have agreed to the wage deal.
The National Employers' Association of South Africa (NEASA), representing about 3,000 employers in the metals sector, said it could not afford the pay rise, which is above the current inflation rate of 6.6 percent.
"We will not sign," NEASA spokesperson Sya van der Walt-Potgieter said, adding that the group's members were being urged to lock out tens of thousands of NUMSA members.
The employers group, whose members employ about 70,000 workers, said it would challenge any attempt to extend the wage agreement to its members.
NUMSA said it was willing to continue talking with NAESA to find a solution to the impasse.
The South African Reserve Bank has expressed concern that pay increases which are not met by gains in productivity could trigger a wage-hike spiral and cost jobs.
The metals and engineering strike came on the heels of a five-month walkout in the platinum sector, the longest and costliest strike in South Africa's history which triggered a contraction in the economy in the first quarter.
The ruling African National Congress (ANC) party has hinted that the government may push forward with reforms to curb the length of strikes.
"It is necessary that a debate must ensue in society on how collectively we find a lasting solution to strikes that last too long," ANC Secretary General Gwede Mantashe said on Tuesday. (Additional reporting by Wendell Roelf and David Dolan; Editing by Joe Brock)