New Zealand First deputy leader and former Carterton Mayor Ron Mark said Mr Walker was doing charitable work in Uganda and was highly respected in his community.
"I've known Geoff for quite a while now," Mr Mark said tonight. "He's respected for having a very strong social conscience. He's a very community-minded person."
He said Mr Walker was working with Lions clubs in Uganda and New Zealand.
"They'd arranged for a young albino boy who was sight-impaired to have an operation, which partially restored his sight."
Mr Mark said "if the stories were true" then Mr Walker had landed in some legal trouble but everybody hoped the situation could be resolved and Mr Walker would return home safely.
"I'm working with the family, who I've known for a while. [It's] fair to say that people are a bit worried."
Hope Sexton, who said she was a relative of Mr Walker, said the family had been in contact with many agencies and were "working tirelessly to try to get in contact with people" in Uganda.
"What we ask is that you are cautious on what you post on social media as any speculation may not be helpful," she posted on Facebook.
"Your continued thoughts and prayers are much welcomed."